Composites including electroconductive reinforcing material formed by electrodeposition and method of forming the composites

ABSTRACT

A method for forming composite material by electrodeposition in which a metal matrix is reinforced by electroconductive filaments. Prior to being fixed to a cathode for encapsulation by the matrix, the filaments are treated so that an electrononconducting film is formed on the surfaces thereof. This insulates the filaments from the electrodeposition process so that the matrix is formed around the filaments without interfering with the matrix buildup so as to encapsulate the filaments free of faulty voids.

Unite States atent [72] Inventor Iqbal Ahmad Elnora, N.Y. [21] Appl. No. 850,696 [22] Filed Aug. 13, 1969 [45] Patented Oct. 26, 1971 [73] Assignee The United States of America as represented by the Secretary of the Army [54] COMPOSITES INCLUDING ELECTROCONDUCTIVE REINFORCING MATERIAL FORMED BY ELECTRODEPOSITION AND METHOD OF FORMING THE COMPOSITES 7 Claims, No Drawings [52] US. Cl 204/38 R, 117/118, 117/121, 148/63, 161/170,204/27 [51] Int. Cl C23b 5/48, B32b 5/00 [50] Field ofSearch 204/10, 12, 16, 38 R, 27

[56] References Cited UNITED STATES PATENTS 2,424,140 7/1947 Beecher 204/16 3,476,529 11/1969 Dubin et a1. 29/192 R X 3,505,177 4/1970 Chester et al.. 204/9 3,061,525 10/1962 Grazen 204/9 3,152,971 10/1964 Tomaszewski et a1. 204/41 3,356,467 12/1967 Brown et al 204/41 X 3,498,890 3/1970 Divecha et a1. 204/16 X OTHER REFERENCES Robinson, Report N. BNWL- SA-550 pp. 10/25/1966 copy in 29- 191,2.

Primary Examiner F. C. Edmundson Attorneys-Harry M. Saragovitz, Edward J. Kelly, Herbert Berl and Albert E. Arnold, Jr.

COMPOSITES INCLUDING ELECTROCONDUCTIVE REINFORCING MATERIAL FORMED lBY ELECTRODEPOSITION AND METHOD OF FORMING THE COMPOSITES The invention described herein may be manufactured, used, and licensed by or for the Government for governmental purposes without the payment to me of any royalty thereon.

BACKGROUND OF THE INVENTION This invention relates to the formation of composite material and pertains more particularly to a method for forming composite material by electrodeposition so as to eliminate faulty voids therein.

The phenomenal progress in space science and technology and the developments in weaponry and logistics during the past two decades have created a pressing demand for materials which have a high strength and modulus-to-density ratio, and high-temperature capability. As a result, a large number of superalloys have been developed. These, however, still fall short of some of the rigorous requirements of the advance engineering concepts.

The availability in recent years of high-strength and hightemperature metallic and ceramic filaments and single crystals have initiated great activity in their utilization as reinforcements of weaker metallic matrices to provide high-temperature, high-strength and lightweight composite materials. A number of techniques are being explored for the fabrication of these reinforced composites. One showing considerable promise is that of electrodeposition because herein the reinforcing particles such as whiskers, fibers and filaments are not subjected to damaging pressures or heat during the formation process. With this technique the reinforcing elements are fixed as a permeable mat or continuous winding to the cathode of an electrolytic apparatus. During electrodeposition, the matrix material passes through the mat or windings of the reinforcing elements to the cathode, building up thereon to gradually encapsulate the reinforcing elements and form the composite material. Trouble, however, has been experienced to a considerable degree with this technique in that when the reinforcing elements are electroconductive they, through their contact with the cathode of the electrolytic apparatus, become cathodic. Thus, the matrix-carrying ions are interrupted by the reinforcing elements while passing therethrough and before reaching the cathode so that the ions deposit on them to form bridges thereacross and thereby create voids thereat.

SUMMARY OF THE INVENTION The problem of void formation in the electrodeposition technique is overcome by the present invention which provides a method for forming by electrodeposition and without faulty voids a composite in which the reinforcing elements are o an electroconductive material. This improves, to make practical, the use of the electrodeposition technique as a means for forming composite material with electroconductive reinforcements. Towards that end, it is an object of this invention to provide a method for forming composite material by electrodeposition in which the matrix is of metal and the reinforcing elements of electroconductive material are rendered nonconductive prior to electrodeposition to thereby eliminate bridging by the matrix across the reinforcing filaments and the fonnation of voids thereat.

It is a further object of this invention to provide a method of fonning composite material by electrodeposition in which the reinforcing elements are provided with an electrononconductive film or coating prior to being fixed to the cathode of the electrolytic apparatus.

It is another object of this invention to provide the reinforcing elements with an electrononconductive coating which detracts very little from the desirable properties thereof.

It is still another object of this invention to form by electrodeposition a composite material comprising reinforcing DESCRIPTION OF PREFERRED EMBODIMENTS The following examples are illustrative of the practice of the invention:

EXAMPLE I An apparatus for the electrodeposition of metal was prepared for forming a composite comprising a nickel matrix reinforced by electroconductive boron filaments. A sulfamate bath was used as the aqueous electrolyte with each gallon containing:

42 oz. of nickel sulfamate 10 oz. of nickel (as metal) oz.

of Boric acid, 7 oz. of nickel bromide (conc.) and 0.06 oz. ofa wetting agent. The bath was diluted to a specific gravity of 293 l Baume scale. The anode wad depolarized nickel and to a flat cathode of stainless steel were attached multilayers of boron filaments which had been previously nitrided to form a nonconductive surface of boron nitride thereon. Attachment was made by use of stopoff lacquer applied to the ends of similar discontinuous lengths of the filaments. The temperature of the bath was maintained during electrodeposition at 50 C. the pH at 38-42 and the current density at 30 a./sq. ft.

When the boron filaments were completely encapsulated, the cathode was removed and the composite material stripped therefrom. Stripping was easily accomplished as the nickel matrix adheres only slightly to the stainless steel cathode and, of course, there was no adherence between the filaments and the cathode. When transverse sections of the composite material were examined it was seen that no nickel had been deposited on the filaments and all voids which had existed in a preliminary experiment under the identical conditions but without the filaments being nitrided, were eliminated.

EXAMPLE II The same apparatus as described in example I with the same sulfamate bath and anode were used in forming a composite of nickel with electroconductive silicon carbide (SiC) filament reinforcement. The SiC filaments were first prepared, before being mounted on the cathode, by heating them at l,l00 C. in a stream of oxygen for a period of 1 minute. The time factor is determined by the temperature at which the filaments are heated, which may be from 900-l,l00 C. It is also effective to previously saturate the oxygen with water at room temperature. By this treatment, a thin (a few microns thick) film of an electrononconductive oxide of silicon was formed on the surfaces. The treatment did not deteriorate the mechanical properties of the filaments to a significant degree. For example, while the tensile strength of the filaments at room temperature was 320,000 p.s.i. before the treatment, the tensile strength of the filaments after treatment was on the average of 300,000 p.s.i.

After formation of the nickel-silicon carbide composite on the cathode, the composite was removed and subjected to examination and again the examination showed that nickel had not formed on the filaments and all voids had been eliminated.

I wish it to be understood that I do not desire to be limited to the exact details of the embodiments of the invention as described, for obvious modifications will occur to a person skilled in the art.

I claim:

l. in the process of forming by electrodeposition means a composite material comprising a metallic matrix with electroconductive reinforcing filaments and said electrodeposition means including a cathode for supporting the reinforcing filamerits and the resulting composite material. the steps of treating said reinforcing filaments so as to be electrically insulated, placing a multifilament layer of said treated filaments on the cathode and plating metal on the cathode to produce a reinforced metal matrix.

2. The process as defined in claim 1 wherein the treatment of said reinforcing filaments comprises forming an electrononconductive film on the surfaces ofsaid reinforcing filaments.

3. The process as defined in claim 2 wherein said reinforcing filaments comprise boron filaments, and the step of treating said reinforcing filaments comprises nitriding said boron filaments to form an electrononconductive film of boron nitride on the surfaces thereof.

4. The process as defined in claim 2 wherein said reinforcing filaments comprise filaments of silicon carbide, and wherein the step of treating said reinforcing filaments comprises forming a film of an electrononconductive oxide of silicon on the surfaces thereof.

5. The process as defined in claim 4 wherein the step comprising forming a film of an electrononconductive oxide of silicon on the surfaces comprises heating said filaments in the presence of oxygen for 1 minute at a temperature of 1,100 C.

6. The process as defined in claim 4 wherein the step comprising forming a film of an electrononconductive oxide of silicon on the surfaces comprises heating said filaments to a temperature of 900-l ,l00 Cr in the presence of oxygen.

7. The process as defined in claim 4 wherein the step comprising forming a film of an electrononconductive oxide of silicon on the surfaces comprises heating said filaments to a temperature of 900-1,l00 Cr in the presence of oxygen previously saturated with water at room temperature. 

2. The process as defined in claim 1 wherein the treatment of said reinforcing filaments comprises forming an electrononconductive film on the surfaces of said reinforcing filaments.
 3. The process as defined in claim 2 wherein said reinforcing filaments comprise boron filaments, and the step of treating said reinforcing filaments comprises nitriding said boron filaments to form an electrononconductive film of boron nitride on the surfaces thereof.
 4. The process as defined in claim 2 wherein said reinforcing filaments comprise filaments of silicon carbide, and wherein the step of treating said reinforcing filaments comprises forming a film of an electrononconductive oxide of silicon on the surfaces thereof.
 5. The process as defined in claim 4 wherein the step comprising forming a film of an electrononconductive oxide of silicon on the surfaces comprises heating said filaments in the presence of oxygen for 1 minute at a temperature of 1,100* C.
 6. The process as defined in claim 4 wherein the step comprising forming a film of an electrononconductive oxide of silicon on the surfaces comprises heating said filaments to a temperature of 900*-1,100* C. in the presence of oxygen.
 7. The process as defined in claim 4 wherein the step comprising forming a film of an electrononconductive oxide of silicon on the surfaces comprises heating said filaments to a temperature of 900*-1,100* C. in the presence of oxygen previously saturated with water at room temperature. 